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The first NASA mission to the moon since 1972 is ready for its most crucial test to date.
The 322-foot-tall (98-meter-tall) Artemis I rocket stack, including NASA’s mega SLS rocket and Orion spacecraft, will begin the wet dress rehearsal Friday. The test is expected to last through Sunday.
The results of the test will determine when the uncrewed Artemis I will launch on a mission that goes beyond the moon and returns to Earth. This mission will kick off NASA’s Artemis program, which is expected to return humans to the moon and land the first woman and the first person of color on the lunar surface by 2025.
The wet dress rehearsal simulates every stage of launch without the rocket actually leaving the launchpad. This includes loading supercold propellant into the rocket’s tanks, going through a full countdown simulating launch, resetting the countdown clock and draining the rocket tanks. The test will begin with a call to stations on Friday at 5 p.m. ET and end Sunday evening with the final countdowns.
The call to stations, which is a check-in with every team associated with a launch, “is a big milestone because it is the time in which we are calling our teams notifying them that the wet dress rehearsal test is officially underway,” said Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, during a news conference Tuesday.
Trial run includes countdown
Once the rocket has been loaded with more than 700,000 gallons (3.2 million liters) of propellant, the teams on Sunday will go through all of the steps toward launch.
“Liquid hydrogen is at a negative 450 degrees Fahrenheit (negative 268 degrees Celsius), liquid oxygen is negative 273 (negative 169 degrees Celsius), so it’s very cold substances,” said Tom Whitmeyer, deputy associate administrator for common exploration systems development at NASA Headquarters during the news conference. “I used to participate in this back in the Shuttle Program and it’s like watching a ballet. You’ve got pressure, volume and temperature. And you’re really kind of working all those parameters to have a successful tanking operation.”
The team members will count down to within a minute and 30 seconds before launch and pause to ensure they can hold launch for three minutes, resume and let the clock run down to 33 seconds, and then pause the countdown.
Then, they will reset the clock to 10 minutes before launch, go through the countdown again and end at 9.3 seconds before launch would occur. This simulates what is called scrubbing a launch, or aborting a launch attempt if weather or technical issues would prevent a safe liftoff.
At the end of the test, the team will drain the rocket’s propellant, just as they would during a real scrub.